Multi-hop wireless communication systems are known as one type of wireless communication system. Communication realized by multi-hop is also referred to as communication by relay.
A multi-hop wireless communication system is a system in which one or a plurality of relay stations are disposed between base stations and mobile terminals of a wireless communication system for the purpose of extending coverage and increasing throughput as well as providing a countermeasure against silent zones. In a multi-hop wireless communication system, a packet from a base station to a mobile terminal is first transmitted from the base station to a relay station and then transmitted from the relay station to the mobile terminal. Similarly, a packet from a mobile terminal to a base station is first transmitted from the mobile terminal to a relay station and then transmitted from the relay station to the base station.
One method for realizing data relay by means of a multi-hop wireless communication system is a method of subjecting wireless frames to time-division in access zones and relay zones (relay areas). In an access zone, a base station and a relay station carry out communication with mobile terminals under the jurisdiction of each base station and each relay station, respectively. In a relay zone, on the other hand, a base station carries out communication with a relay station and mobile terminal that is under its jurisdiction, and a relay station carries out communication with a higher-order base station or relay station (higher-order station). When two or more relay stations are present between a base station and a mobile terminal, the relay station carries out communication with the relay station that is under its jurisdiction in a relay zone. Patent Document 1 gives an example of a multi-hop wireless communication system that is based on a WiMAX (Worldwide Interoperability for Microwave Access) system.
In recent years, femtocells are coming into use in wireless communication systems. A wireless communication system that is realized by femtocells provides wireless communication services by means of femto base stations for ranges that are narrower than cells (referred to as a macrocells) that are provided by a typical base station or relay station. A femto base station is installed outside macrocells or in sites in which macrocell radio waves are hard to reach such as, principally, in buildings, and is used for complementing wireless communication services realized by macrocells.